"She only wants half a piece of cake."

Translation: 她只要半块蛋糕。

[PeaceJoyPancakes]

Well, then, we have a real conundrum. A piece is a piece, whatever the size. Cut it in half and you have two whole pieces. Then what?

[orgat]

Hahaha good point.
However, I think what they were trying to say is "half a slice".
(If the cake has already been sliced to slices, and you want just half a slice)

[PeaceJoyPancakes]

So you slice yourself a slice that's half as large as the original slice? I'm not sure that solves the problem...

But I'm just fooling around.

[badwolfnorth]

“她只想半块蛋糕”

Any reason 想 can't work here?

[PeaceJoyPancakes]

"想" has to be followed by a verb to mean "to want (to)". In front of a noun it doesn't mean "to want" in the English sense of "to be thinking of having". Instead it means "to miss (someone or something)", "to think up (an idea)", etc. Your sentence makes it sound as though she misses the cake.

[KX3.]

It works if you say 想要

[Celticfiddleguy]

Yes, but "我只想要" sounds a little awkward to me. (I'm not sure tho, maybe a native speaker can comment on this?)

[PeaceJoyPancakes]

KX3 is a native speaker. I imagine you'll get your wish. (Sounds okay to me though.)

[KX3.]

It is not as common but still colloquial. I was just a little surprised it wasn't used at all here, but then again their conception of 想、很、要 and such is a little different from what is normal for me and a others here.

[RobertEddy]

Sounds likr my Grandmother.

[Karoliina765050]

Could I say 她只要一半块蛋糕?

[KX3.]

No, you can say 她只要那块蛋糕的一半。 if you want to use 一半 and it would translate as something like "...half a piece of that cake".

[maartendoc]

蛋 (dàn) = egg/oval-shaped thing
糕 (gāo) = cake
蛋糕 (dàngāo) = cake

Two version of kuài that we learned:
快 (kuài) = rapid/quick/speed
块 (kuài) = chunk/piece/classifier for cloth, cake, soap/classifier for money

[WangShu412]

Only half of a piece of cake?? The treachery...

[camilomezu]

Why is the 快 there?

[NathanRasm]

'piece'

But it's 块 not 快.